Vent valve for gas pressure regulators and pressure regulator equipped with said vent valve

ABSTRACT

The invention is a gas vent valve ( 10 ) for a gas pressure regulator ( 1 ), comprising: a tubular body ( 11 ) developed between two opposite openings ( 11   a,    11   b ); a shutter body ( 12 ) biased towards a position in which a first opening ( 11   a ) of the tubular body ( 11 ) is closed and movable from the closed position towards an open position for opening the first opening ( 11   a ) due to the effect of a pressure acting from the outside of the tubular body ( 11 ) through the first opening ( 11   a ); constraining means ( 13 ) configured so as to prevent the movement of the shutter body ( 12 ) from the closed position towards the open position when the ambient temperature exceeds a predefined value.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Italian Application No.VI2015A000016, filed Jan. 21, 2015, which is incorporated herein byspecific reference.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention concerns a vent valve for gas pressure regulatorsof the type used for the distribution of natural gas. The presentinvention concerns also a pressure regulator using said vent valve.

2. Relevant Technology

As is known, in the distribution of natural gas, pressure regulators areused to maintain the pressure of the delivered gas at a substantiallyconstant value, independently of the flow rate drawn by the users.

A regulator of the above mentioned type typically comprises acontainment body defining a gas flow duct, along which a movable shutteris arranged.

The containment body defines also a motorization chamber containing amembrane that divides the volume of the chamber in a first zone underthe same pressure as the gas in the flow duct downstream of the shutter,and in a second zone that is under atmospheric pressure thanks to thepresence of a vent hole.

Said vent hole ensures that the membrane can move freely due only to theeffect of the variations in the gas pressure at the outlet of theregulator.

The membrane is associated with a preload spring that determines thedelivery pressure of the regulator.

The membrane is associated with the shutter in such a way as to transferits movements to the latter, so that the shutter increases or decreasesits degree of opening depending on demand by the users.

The vent hole has a sufficiently limited cross section for the passageof the gas, in order to prevent the membrane from oscillating in thepresence of sudden variations in the flow rate of the delivered gas, asa consequence of the so-called “pumping” effect, which would make theoperation of the regulator unstable.

Said limited cross section of the vent hole, however, poses the drawbackthat it prevents any rapid movements of the membrane, which would benecessary in case of important flow rate variations, for example thosecaused by the start or the stop of a heating boiler.

The drawback described above can be overcome by providing the pressureregulator with a vent valve arranged in parallel with said vent hole,normally closed and configured so that it opens when the pressure in thesecond zone of the motorization chamber exceeds a predefined value dueto a wide and rapid movement of the membrane.

Said vent valve, however, poses the drawback that it allows the gas toflow out of the regulator in case of breakage of the membrane, which canrepresent a risk in terms of safety, especially when the regulator isexposed to high temperatures.

It is known that in order to overcome said drawback the regulator isprovided with a second safety membrane.

However, the technique just described above is not effective in thepresence of temperatures that are such as to cause both membranes tocollapse.

It is known that in order to overcome said drawback a vent duct is usedfor the purpose of placing the outlet of the vent means in communicationwith a zone in which a possible release of gas in the atmosphere wouldnot generate safety risks.

The known technique just described above, however, poses the drawback ofbeing expensive to implement, considered that it requires an additionalvent duct that, among other things, can be considerably long.

A further drawback posed by the above mentioned technique lies in thatthe presence of the vent duct involves a pressure drop that may affectthe correct operation of the vent valve.

According to a known technique that represents an alternative to the onepreviously described, a pressure regulator is used that is oversizedcompared to the needs and is provided with a membrane whose dimensionsare such that the maximum gas pressure variation allowable duringoperation causes just a small movement of the membrane, which can bemanaged by means of the vent hole only, with no need to provide also avent valve.

Also this second known technique, however, poses the drawback of beingrather expensive, due to the higher cost of the oversized pressureregulator.

SUMMARY OF THE INVENTION

The present invention intends to overcome all the said drawbacks relatedto the known techniques.

In particular, it is the object of the present invention to allow theuse of a pressure regulator that is sized according to the flow rate tobe delivered and that ensures the same performance levels as ananalogous pressure regulator provided with a vent valve, while at thesame time limiting the maximum gas flow rate discharged towards theoutside of the regulator in the presence of temperatures exceeding apredefined safety threshold.

Said object is achieved by a vent valve constructed in accordance withclaim 1.

Said object is also achieved by a pressure regulator constructed inaccordance with claim 9.

Further characteristics and details of the invention are provided in therespective dependent claims.

Advantageously, the invention eliminates the need to provide for thepresence of a duct that connects the vent valve to a safety zone.

Still advantageously, the invention eliminates the need to use aregulator that is oversized compared to the needs.

Consequently, the invention advantageously makes it possible to limitthe costs related to the pressure regulator compared to those related tothe known techniques described above, at least in those applications inwhich it is necessary to limit the flow rate of the gas deliveredoutside of the regulator in high temperature conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

The said objects and advantages, together with others that will beillustrated here below, are highlighted in the description of apreferred embodiment of the invention, which is provided by way ofexample without limitation with reference to the attached drawings,wherein:

FIG. 1 shows a sectional view of the pressure regulator that is thesubject of the invention;

FIG. 2 shows a sectional view of the vent valve that is the subject ofthe invention;

FIG. 3 shows a top view of the valve shown in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The vent valve that is the subject of the invention will be describedwith reference to a gas pressure regulator indicated as a whole by thereference number 1 in FIG. 1.

The pressure regulator 1 comprises a containment body 2 that defines aflow duct 3 for said gas and a motorization chamber 4 that communicateswith the flow duct 3, for example through a passage hole 27.

The flow duct 3 comprises a section under high pressure 3 a, to whichthe gas supply line is connected, and a section under low pressure 3 b,to which the duct conveying the gas to the user device is connected.

A shutter 9 is interposed between said two sections 3 a, 3 b, creating abottleneck with adjustable cross section that makes it possible toadjust the gas pressure drop between the two sections.

The shutter 9 is associated with a first membrane 7 arranged in saidmotorization chamber 4 in such a way as to divide the latter in a firstzone 4 a, which is placed in communication with the flow duct 3, and asecond zone 4 b, which communicates with vent means 5 in turncommunicating with the outside of the containment body 2.

In particular, the shutter 9 is operatively associated with the firstmembrane 7 in such a way that the movements of the latter in twoopposite directions cause corresponding movements of the shutter 9 thatare intended to increase or, respectively, decrease the cross section ofthe gas passage along the flow duct 3.

In the example illustrated in FIG. 1, lifting the first membrane 7closes the shutter 9, and vice versa.

The membrane 7 is associated with elastic means 28, typically comprisinga spring that counteracts the action of the gas pressure in the secondzone 4 b of the motorization chamber with a force that is proportionalto the gas pressure that the pressure regulator 1 needs to maintain inthe low pressure section 3 b of the flow duct 3.

As far as the vent means 5 are concerned, these comprise a vent hole 6that places the second zone 4 b of the motorization chamber 4 inpermanent communication with the outside of the containment body 2.

Said vent hole 6 makes it possible to constantly maintain the membraneside facing towards the second zone 4 b of the motorization chamber 4under atmospheric pressure, thus allowing the air to be vented out ofthe second zone 4 b according to the variations in the volume of thelatter resulting from the movements of the first membrane 7.

Preferably, the vent hole 6 has a reduced cross section for the passageof gas, preferably smaller than 1 mm², in such a way as to limit themaximum gas flow rate that can be let out of the pressure regulator 1 incase of failure of the regulator itself, for example in case of breakageof the first membrane 7.

Preferably, the regulator 1 comprises a second membrane 8 interposedbetween said first membrane 7 and the vent means 5.

Advantageously, said second membrane 8 makes it possible to preserve thefunctionality of the regulator 1 also in case of breakage of the firstmembrane 7, until the replacement of the regulator 1.

Preferably, the second membrane 8 is provided with a hole suited toprevent the formation of an air cushion with the first membrane andhaving a diameter that is such as to limit the release of gas throughthe vent hole 6 to a flow rate deemed safe.

The vent means 5 comprise also a vent valve 10 that, as shown in greaterdetail in FIG. 2, comprises a tubular body 11 for the passage of air,provided with two openings 11 a, 11 b located opposite each other.

The first opening 11 a is in communication with the motorization chamber4 of the pressure regulator 1, while the second opening 11 b facestowards the outside of the pressure regulator 1 and is preferablyprotected by a filter 22 that prevents the penetration of impurities inthe valve.

The vent valve 10 comprises also a shutter body 12, configured in such away that it can spontaneously assume a position in which a first one ofsaid two openings 11 a is closed and that it can be moved from theclosed position towards an open position of the first opening 11 a dueto the effect of a pressure acting from the outside of the tubular body11 through the first opening 11 a itself.

Preferably but not necessarily, said shutter body 12 is a ball that, dueto the effect of its own weight, spontaneously comes to be positioned atthe bottom, so as to close the first opening 11 a, but is raised by asufficient pressure that is exerted through the latter.

Advantageously, said vent valve 10 allows the first membrane 7 of theshutter 9 to perform sudden and relatively large movements in thedirection corresponding to the reduction in the volume of the secondzone 4 b of the motorization chamber 4, upwards in the case at hand.

Said movements are, typically, those corresponding to a sudden reductionin the flow rate of operative gas following a corresponding reduction indemand by the users. Said phenomenon takes place, for example, in theheating boilers when they are switched off.

In particular, an interruption in the demand by the users causes apressure impulse in the second section 3 b of the flow duct 3 of theregulator 1 which causes the development, on the first membrane 7, of acorresponding pressure that tends to move it in the directioncorresponding to the reduction in the volume of the second zone 4 b ofthe motorization chamber 4, consequently producing an overpressuretherein.

This last overpressure lifts the shutter body 12 of the vent valve 10,thus allowing the excess air to flow towards the outside of themotorization chamber 4 so that the air itself does not hinder the rapidupward movement of the first membrane 7.

When the first membrane 7 is going to reach the new balance position, inwhich the pressure in the second zone 4 b counterbalances the force ofthe spring 28, said overpressure is reduced to such a level that theshutter body 12 spontaneously closes the first opening 11 a. In thiscondition, the passage of air between the second zone 4 b and theoutside takes place only through the vent hole 6 whose reduced crosssection, considerably smaller than the gas passage cross section of thevent valve 10 in the open configuration, prevents the triggering of thepumping effect described above.

According to the invention, the vent valve 10 comprises constrainingmeans 13 configured to prevent the movement of the shutter body 12 fromthe closed position towards the open position when the ambienttemperature exceeds a predefined value.

In case of breakage of the first membrane 7 and, if present, of thesecond membrane 8 of the pressure regulator 1 in high temperatureconditions, said constraining means 13 prevent the vent valve 10 fromallowing the release of a high gas flow rate towards the outside, withpotentially dangerous consequences.

In fact, when the temperature reaches said predefined value, the ventvalve 10 is inhibited and any gas leakages must necessarily pass throughthe vent hole 6, which limits their flow rate to levels that are notdeemed dangerous.

Preferably, said predefined value is lower than 150° C. and, even morepreferably, it is included between 110° C. and 130° C.

Still preferably, the second membrane 8 of the regulator 1 or, if thisis absent, the first membrane 7, is made in such a way that it resists atemperature exceeding the predefined collapse value.

In this way, advantageously, leakages from the regulator 1 at a high gasflow rate will be avoided in the case where the membranes 7, 8 shouldcollapse due to an excessive temperature.

In fact, when the temperature that causes the collapse of the membranes7, 8 is reached, the constraining means 13 have already intervened andthe vent valve 10 is therefore already blocked.

Preferably and as shown in detail in FIG. 2, the constraining means 13comprise thrust means 14 suited to maintain the shutter body 12 in theclosed position, and stop means 15 suited to inhibit the thrust means 14and configured so as to release the latter when the ambient temperatureexceeds said predefined value.

Preferably, the thrust means 14 comprise a shaped body 16 associatedwith elastic means 17 suited to thrust it against the shutter body 12 soas to force it in the closed position.

As far as the stop means 15 are concerned, these preferably comprise acounteracting body 18 constrained to the tubular body 11 and suited tocounteract the action of the elastic means 17 in order to maintain theshaped body 16 in a spaced position with respect to the shutter body 12and configured so that it yields when the ambient temperature exceedsthe predefined value.

Advantageously, said configuration makes it possible to produce a ventvalve 10 that is effective, reliable and simple to manufacture.

Preferably, the counteracting body 18 rests on a reference partition 25belonging to the tubular body 11 and comprising one or more holes 26 forthe passage of air, visible in FIG. 3 which, for the sake of clarity,shows the vent valve 10 without the filter 22.

Preferably, the counteracting body 18 is associated with the shaped body16 through a counter thread 20 screwed to a corresponding thread 19belonging to the shaped body 16.

Advantageously, the configuration just described above facilitates theassembly of the vent valve 10 and simplifies its construction.

Regarding the elastic means 17, these preferably comprise a spring.

Regarding, on the other hand, the counteracting body 18, this ispreferably made of a plastic material, even more preferably anacetal-based or nylon-based material, filled so as to provide it withthe desired heat resistance characteristics.

Preferably, the tubular body 11 of the vent valve 10 comprises anexternal thread 21 suited to be screwed into a threaded hole provided inthe pressure regulator 1.

Advantageously, said external thread 21 allows the vent valve 10 to becoupled with most pressure regulators 1, exploiting the threadedinspection hole with which most of the regulators available on themarket are provided.

Preferably but not necessarily, the tubular body 11 is constituted bytwo distinct portions 23, 24, wherein one of the two portions 24comprises the external thread 21.

Advantageously, the structure of the tubular body 11 divided in twoportions as described above facilitates the coupling of the vent valve10 with various pressure regulators 1 that differ from one another forthe thread provided in the hole housing the vent valve 10.

In fact, the portion 24 of the tubular body 11 can be made in severalvariants, all of which can be coupled with the portion 23 of the tubularbody 11, but each one of which is provided with a corresponding externalthread 21 that is different from the external thread of the othervariants.

In the light of the description provided above, it can be understoodthat the vent valve and the pressure regulator equipped with said valveachieve the set object.

In fact, the vent valve allows the rapid movement of the membrane of theregulator in the presence of considerable and rapid variations in therequired gas flow rate, at the same time preventing the outflow of gasin temperature conditions deemed unsafe but avoiding the need to use avent duct to convey the gas from the valve to a safe area, or anoversized regulator, thus making it possible to limit costs.

The invention claimed is:
 1. A gas vent valve for a gas pressureregulator, comprising: a tubular body provided with a first opening anda second opening opposite thereof; a shutter body movably mounted tomove between a closed position, in which said shutter body closes saidfirst one opening, and an open position, in which said shutter bodyopens said first opening, said shutter body being constantly biasedtowards said closed position, said shutter body being biased towardssaid open position upon a pressure acting from the outside of saidtubular body through said first opening, wherein said second opening isin communication with said first opening so that, when a gas coming fromsaid first opening opens said shutter body, said gas flows through saidsecond opening; and further comprising constraining means for preventingsaid shutter body from moving from said closed position towards saidopen position when the ambient temperature exceeds a predefined value,said constraining means comprising: thrust means at least partiallydisposed within said tubular body and suited for maintaining saidshutter body in said closed position, said thrust means being disposedbetween said first opening and said second opening; and stop meanssuited for inhibiting said thrust means, said stop means beingconfigured so as to release said thrust means when the ambienttemperature exceeds said predefined value.
 2. The gas vent valveaccording to claim 1, wherein said thrust means comprise a shaped bodyassociated with elastic means suited for thrusting said shaped bodyagainst said shutter body, said stop means comprising a counteractingbody constrained to said tubular body and suited to maintain said shapedbody in a spaced position with respect to said shutter body against theaction of said elastic means, said counteracting body being configuredto yield when the ambient temperature exceeds said predefined value. 3.The gas vent valve according to claim 2, wherein said shaped bodycomprises a thread, said counteracting body comprising a counter threadscrewed to said thread.
 4. The gas vent valve according to claim 2,wherein said elastic means comprise a spring.
 5. The gas vent valveaccording to claim 2, wherein said counteracting body is made of aplastic material.
 6. The gas vent valve according to claim 5, whereinsaid plastic material is a acetal-based or nylon-based material.
 7. Thegas vent valve according to claim 1, wherein said tubular body comprisesan external thread so that said tubular body can be screwed to apressure regulator.
 8. A gas pressure regulator comprising: acontainment body that defines a flow duct for a gas and a motorizationchamber communicating with said flow duct; vent means suited for placingsaid motorization chamber in communication with the outside of saidcontainment body and comprising a vent hole suited to place saidmotorization chamber in permanent communication with the outside of saidcontainment body; a first membrane arranged in said motorization chamberin such a way as to divide said motorization chamber into a first zone,communicating with said flow duct, and into a second zone, communicatingwith said vent means; a shutter arranged in said flow duct andassociated with said first membrane in such a way that the movements ofsaid first membrane in two opposite directions cause correspondingmovements of said shutter intended to increase or, respectively,decrease a gas passage cross section along said flow duct, wherein saidgas vent means comprise a vent valve according to claim
 1. 9. Theregulator according to claim 8, wherein said vent hole has a smaller gaspassage cross section compared to that of said vent valve.
 10. Theregulator according to claim 8, further comprising a second membraneinterposed between said first membrane and said vent means and beingconfigured so as to resist a temperature exceeding said predefinedvalue.
 11. The gas vent valve according to claim 1, further comprising agas pressure regulator secured to the tubular body.
 12. A gas pressureregulator comprising: a containment body having an inlet, an outlet, anda flow duct that extends therebetween, the containment body also havinga motorization chamber; a first membrane disposed within the containmentbody and dividing the motorization chamber into a first zone thatcommunicates with the flow duct and a second zone; a shutter disposed inthe flow duct and associated with the first membrane so that movement ofthe first membrane in two opposite directions causes correspondingmovement of the shutter; and a first gas vent valve comprising: atubular body having a first opening and a second opening spaced apartfrom the first opening, the tubular body being secured to thecontainment body so that the first opening is in communication with thesecond zone of the motorization chamber; a shutter body movable betweena first position wherein the shutter body closes the first opening and asecond position wherein the shutter body opens the first opening, theshutter body being resiliently biased towards the closed position, thefirst opening being in communication with the second opening when theshutter body is in the second position; and a constraining member thatprevents the shutter body from moving from the first position toward thesecond position when the ambient temperature exceeds a predefined value,the constraining member comprising: a thrust member at least partiallydisposed within the tubular body and suited for maintaining the shutterbody in the closed position, the thrust member being disposed betweenthe first opening and the second opening; a stop member that inhibitsmovement of the thrust member, the stop member releasing the thrustmember when the ambient temperature exceeds the predefined value; and aspring that moves the thrust member when the thrust member is releasedby the stop member, the spring forcing the thrust member against theshutter body so as to hold the shutter body in the first position. 13.The gas pressure regulator according to claim 12, further comprising asecond vent valve spaced apart from the first vent valve, the secondvent valve being in communication with the second zone of themotorization chamber.